1. Field of the Invention
The present invention relates to a system LSI including a logic circuit section and an input/output section having a plurality of I/O cells, and particularly relates to a system LSI including a circuit which uses an I/O power source as well as the I/O cells.
2. Background Art
System LSIs in recent years employ a structure in which I/O cells (an input/output section) for input/output are arranged around an LSI and are driven by an I/O power source (at 2.5 V, for example) while logic cells or RAM cells (a logic circuit section) which operate at low voltages are arranged within a range surrounded by the I/O cell group and are driven by a CORE power source (at 1.0 V, for example).
Also, electric fuse circuits have been employed conventionally as programming devices for redundancy relief in memories and the like (see Published Japanese Translation of PCT International Application No. 11-512879). Though voltages higher than that used in ordinary MOS transistors had been required for programming the conventional electric fuse circuits, progress in miniaturization in recent years in the 130 nm process generation enables a fuse element formed of a gate material to be programmed with the use of a power source (an I/O power source) of which power an input/output circuit consumes usually.
Consider here the case where an electric fuse circuit which uses an I/O power source as a power source for programming is arranged in a system LSI and is connected to the power source. In this case, it is necessary to draw a power source line from an I/O power source cell to a logic circuit section and to extend it to the electric fuse circuit for connection.
While, for programming the electric fuse circuit, an electric current of approximately 10 to 20 mA is necessary. For this reason, the power source line from the I/O power cell to the electric fuse circuit should have low impedance, and therefore, has a wide width. This is unfavorable in view of area efficiency of the system LSI. This problem may occur not only with the electric fuse circuit but also with any other circuits using the I/O power source as a power source.